This year Closed Joint-Stock Company Northern Urals Gold, a subsidiary of Polymetal Inter-Regional Research and Production Association started its season earlier than usual.
Closed Joint-Stock Company Northern Urals Gold, which is a subsidiary of Polymetal Inter-Regional Research and Production Association in Saint-Petersburg, and mines Vorontsovskoye, the largest deposit in Sverdlovsk region, recovering gold using the heap-leaching method, opened a new season 15 April, by starting the filling of ore into new stock heaps.
The first thousands tons of ore lie at the base of the heap formed in the new season. About 4 thousand tons of ore prepared for leaching will be added to the heap daily. Leaching is one of the most important technological stages of gold mining. During this stage, gold contained in ore passes into liquid fraction, as a result of irrigation with working solutions, and becomes available for recovery.
The method of heap leaching was invented in 1969 and has become more and more widespread because it makes gold recovery possible, even from low-grade ores. The method is based on the original gold extraction method from ore by cyanidation, which was patented in 1887. With the help of this method about 92% of ore gold was extracted over the last 20 years. (Mining Magazine, May 2001, pp 256-261.) Preparations for the new season were ongoing throughout winter. The equipment for heap filling was prepared, the section of ore-preparation was upgraded, stripping was conducted and ore deposits were also prepared for development.
Thus, 200 tons of ore are now ready for loading. As practice shows, preliminary preparation and storage of ore during the winter period, is inexpedient, as rock freezes solid under the harsh climatic conditions, and becomes open to use only at the beginning of summer, when it completely thaws. By the end of the season, it is anticipated that no less than 600 thousand tons of ore will be extracted and laid in heaps.
The unique technologies of intrastack irrigation and heating of the technological solutions in heat exchangers which are applied at Vorontsovskoye deposit, make it possible not to interrupt the gold mining process in winter time, and to carry out the heap-leaching process all year round, even in regions with a severe climate. As a result of this, in the first quarter of 2002 Closed Joint-Stock Company Northern Urals Gold sent 257 kg of gold and 460 kg of silver to refining factories. Vorontsovskoye deposit is located in Krasnoturinsk district of Sverdlovsk region. Its development began in 1999.
During the first stage of the deposit"s exploitation, processing of oxidized ores was carried out. Today, pilot-scale production of gold from oxidized ores using the heap-leaching method is being developed. Currently, a project for the "First phase of Vorontsovskoye deposit development" is being prepared. It includes mining and processing of oxidized ores in particular.
The next stage incorporates designing and construction of the second phase of mining and processing of primary ores. Mineable reserves of the deposit make up 76.4 tons of silver and 62.4 tons of gold. The annual output of the enterprise is six hundred thousand tons of ore. Preparation of additional areas for heaps continues, construction of a third storage tank for production solutions, with a volume of 6 thousand cubic meters, is near completion. The multistage system of isolation applied during its construction, and the closed cycle of use of production solutions, exclude any possibility of industrial components penetrating into the environment.
source: Polymetal press-release, 15.04.2002